1. Field of the Invention
The present invention relates to a damper mechanism. More specifically, the present invention relates to a damper mechanism that damps torsional vibrations in a power transmission system.
2. Background Information
Clutch disk assemblies used in vehicles function as a clutch for engaging and disengaging the flywheel to facilitate the transfer of torque from an engine. Clutch disk assemblies also function as a damper mechanism for absorbing and damping torsional vibrations from the flywheel. In general, vehicle vibrations include idling-related noises such as rattling sounds, traveling-related noises such as rattling associated with acceleration and deceleration and muffled noises, and tip-in-tip-out or low frequency vibrations. The damper function of the clutch disk assembly is provided ideally to eliminate these noises and vibrations.
Idling-related noises are rattling noises that emit from the transmission when the gearshift is put into neutral and the clutch pedal is released. For example, while waiting at a traffic light a driver might shift the gear into neutral, causing the transmission to rattle. When the engine is running at a speed in the vicinity of idling speed, the engine torque is relatively low and the torque change at the time of power stroke explosion is relatively large. Thus, the aforementioned noises are caused. Under these conditions, the teeth of the transmission input gear and counter gear undergo a phenomenon of striking against one another.
Tip-in and tip-out or low frequency vibrations refer to large-scale lengthwise shaking of the vehicle that occurs when the accelerator pedal is depressed or released suddenly. If the rigidity of the drive transmission system is low, the torque transmitted to the tires is transmitted back from the tires as torque and the resulting lurching reaction causes excessive torque to be generated at the tires. As a result, longitudinal vibrations occur that shake the vehicle excessively back and forth.
In the case of idling noises, the problem lies in the zero torque region of the torsion characteristic of the clutch disk assembly. This problem is alleviated if the torsional rigidity is low. Conversely, it is necessary for the torsion characteristic of the clutch disk assembly to be as rigid as possible to suppress the longitudinal vibrations caused by tip-in and tip-out.
In order to solve this problem, a clutch disk assembly has been proposed which has a two-stage characteristic obtained by using two types of spring members. The first stage or low twisting angle region of the torsion characteristic has a relatively low torsional rigidity and low hysteresis torque, and provides a noise preventing effect during idling. Meanwhile, the second stage or high twisting angle region of the torsion characteristic has a relatively high torsional rigidity and high hysteresis torque. Thus, the second stage is sufficiently capable of damping the longitudinal vibrations of tip-in and tip-out.
A damper mechanism that efficiently absorbs small torsional vibrations during the second stage of the torsion characteristic is also known. By not allowing the large friction mechanism of the second stage to operate when small torsional vibrations are inputted due to such factors as combustion fluctuations in the engine the damper mechanism absorbs small torsional vibrations.
In order to prevent the large friction mechanism of the second stage from operating when small vibrations are transmitted due to, for example, engine combustion fluctuations while the damper mechanism is in the second stage of its torsion characteristic, it is necessary for the high-rigidity spring member to be compressed and for a rotational gap of a prescribed angle to be secured between the high-rigidity spring member and the large friction mechanism. The angular magnitude of this rotational gap is small, i.e., approximately 0.2 to 1.0 degrees. The rotational gap exists in both the positive side second stage and the negative side second stage. The positive side second stage corresponds to when the input plate (input rotary member) is twisted in the rotational drive or positive direction with respect to the spline hub (output rotary member). The negative side second stage corresponds to when the input plate is twisted in a direction opposite the rotational drive direction (negative direction) with respect to the spline hub. Conventionally, the rotational gap is achieved using the same mechanism on both the positive side second stage and the negative side second stage. Consequently, a rotational gap is always produced on both the positive twisting side and the negative twisting side of the torsion characteristic. Further, the angular magnitude of the gap is identical on both sides. However, there are situations where it is preferred that the magnitude of the rotational gap be different on the positive and negative sides of the torsion characteristic. It is also possible to have a situation where it is desirable not to provide the rotational gap at all on one side, i.e., either the positive side or the negative side.
More specifically, it is necessary to have a rotational gap on the negative side of the torsion characteristic in order to reduce the peak vibrations that occur at resonance rotational speed during deceleration. However, in FF vehicles, the resonance peak often remains in the region of practical engine speeds. Further, the noise and vibration control in the vicinity of the resonance rotational speed worsen if a rotational gap is provided on the positive side of the torsion characteristic.
In view of the above, there exists a need for a damper mechanism that overcomes the above-mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to improve the noise and vibration controls of a damper mechanism having a low-hysteresis-torque generation gap as a measure against small torsional vibrations.
A damper mechanism in accordance with a first aspect of the present invention is configured to be used in a vehicle transmission system, preferably a power transmission system to facilitate the transfer of torque from an engine flywheel. The damper mechanism is also configured to dampen and absorb torsional vibrations from the flywheel. The damper mechanism has an input rotary member, an output rotary member, a damper section, a friction mechanism, and a friction suppressing mechanism. The output rotary member is arranged such that it can rotate relative to the input rotary member. The damper section has an elastic member, preferably a spring, and a torsion characteristic. The elastic or spring member rotationally couples the input rotary member and output rotary member together. The torsion characteristic has a positive side and a negative side. The positive side corresponds to the input rotary member being twisted in a rotational drive direction with respect to the output rotary member. The negative side corresponds to the input rotary member being twisted in a direction opposite the rotational drive direction with respect to the output rotary member. The friction mechanism can generate friction when the input rotary member and output rotary member undergo relative rotation and the spring member exerts an elastic force. The friction suppressing mechanism secures a rotational gap on one side only, i.e., the positive side or the negative side, of the torsion characteristic to prevent the elastic force of the spring member from acting on the friction mechanism within a prescribed angular range.
The friction suppressing mechanism of this damper mechanism secures a rotational gap to prevent the friction mechanism from operating on only the positive side or only the negative side of the torsion characteristic. Thus, the noise and vibration controls of the vehicle during both acceleration and deceleration are enhanced because the rotational gap is provided on either the positive side or the negative side of the torsion characteristic, depending on the characteristics of the vehicle.
A damper mechanism in accordance with a second aspect of the present invention is the damper mechanism of the first aspect, wherein the friction suppressing mechanism secures the rotational gap only on the negative side of the torsion characteristic. In this damper mechanism, the rotational gap for preventing the friction mechanism from operating is provided only on the negative side of the torsion characteristic. Thus, deterioration of the noise and vibration controls in the vicinity of the resonance rotational speed on the positive side is suppressed when this damper mechanism is used in, for example, a FF vehicle for which the resonance peak remains in the region of practical engine speeds. As a result, the noise and vibration controls of the vehicle during both acceleration and deceleration are improved.
A damper mechanism in accordance with a third aspect of the present invention is configured to be used in a vehicle transmission system, preferably a power transmission system to facilitate the transfer of torque from an engine flywheel. The damper mechanism is also configured to damper torsional vibrations from the flywheel. The damper mechanism has an input rotary member, an output rotary member, a damper section, a friction mechanism, and a friction suppressing mechanism. The output rotary member is disposed such that it can rotate relative to the input rotary member. The damper mechanism has a spring member and a torsion characteristic. The spring member rotationally couples the input rotary member and output rotary member together. The torsion characteristic has a positive side and a negative side. The positive side corresponds to the input rotary member being twisted in a rotational drive direction with respect to the output rotary member. The negative side corresponds to the input rotary member being twisted in a direction opposite the rotational drive direction with respect to the output rotary member. The torsion characteristic also has a first stage and a second stage. The second stage corresponds to the spring member being compressed. Further, the second stage has a higher rigidity than the first stage. A second stage exists on both the positive side and the negative side of the torsion characteristic. The friction mechanism can generate friction when the input rotary member and output rotary member rotate relative to each other within the second stage. Further, the spring member exerts an elastic force. The friction suppressing mechanism secures a rotational gap at only the second stage on the positive side or the second stage on the negative side of the torsion characteristic to prevent the elastic force of the spring member from acting on the friction mechanism within a prescribed angular range.
The friction suppressing mechanism of this damper mechanism secures a rotational gap to prevent the friction mechanism from operating in the second stage on only the positive side or only the negative side of the torsion characteristic. Thus, the damper mechanism can improve the noise and vibration controls of the vehicle during both acceleration and deceleration by providing the rotational gap at either the second stage on the positive side or the second stage on the negative side of the torsion characteristic in accordance with the preferred characteristics of the vehicle.
A damper mechanism in accordance with a fourth aspect of the present invention is the damper mechanism of the third aspect, wherein the friction suppressing mechanism secures the rotational gap only in the second stage on the negative side of the torsion characteristic. In this damper mechanism, the rotational gap for preventing the friction mechanism from operating is provided only for the second stage on the negative side of the torsion characteristic. Thus, deterioration of the noise and vibration controls in the vicinity of the resonance rotational speed on the positive side is suppressed when this damper mechanism is used in, for example, a FF vehicle for which the resonance peak remains in the region of practical engine speeds. As a result, the noise and vibration controls of the vehicle during both acceleration and deceleration are improved.
These and other objects, features, aspects, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.